How can I send a welcome email from customers that sign-up on a POS transaction

[cwemiwgans]

Hi,

I want to send a welcome email after a new customer signs up during a POS transaction and consents to receive newsletters etc. 

I am using Omnisend at the moment. I tried to create an automation workflow using tags but when customers sign up from the online store or POS are tagged the same, source:shopify.

If there is another way, any help is appreciated!